So after mulling it over some more and hanging out in the SH thread I wanted to say a little more on what they could do to fix this, something more coherent and less emotional. Its more rehashing yea but I felt the need to say it anyway.

They should really have kept all the poly stuff locked behind dialogue that Tav initiates. Tav has the option to express poly relationships even in act 2, so the whole thing should have been focused on player input rather than companion characterization anyway.

In regards to Halsin, while having a conversation with him about mono isnt bad...it feels yucky. I dont want to ask, beg, pressure, or manipulate him. I want him to want to be mono with me. I dont want to maniplulate him the way we feel he manipulated us.

The only time Halsin or any of the companions should be open to a polyship, is if Tav suggests it. If Tav solo romances him, or breaks it off with whoever they are romancing to be with him, that should be the end of it. So when you ask for the status of the relationship, unless you are already playing poly, he shouldnt talk about fluidity and stuff like that, as its no longer part of his character and is off the table. He should not be saying monogamy isnt for him. If Tav decides to reopen the relationship, fine. But if Tav hasnt explicitly said anything about going poly, the default should be mono. This makes sense narratively as he says "I only want you" and gives the player complete agency and control which is the main issue for this character.